Electromagnetic radiation emission device for generating black body electromagnetic radiation



Dec. 30, 1969' A. .1. CUSSEN 3,487,217

ELECTROMAGNETIC RADIATION EMISSION DEVICE FOR GENERATING BLACK BODYELECTROMAGNETIC RADIATION Filed Jan. 17. 1966 2A 28 25*; zeiamlINVENTOR. ART/114R J. CussfN A TT'ORNELY Patented Dec. 30, 1969 US. Cl.250-85 Claims ABSTRACT OF THE DISCLOSURE There is disclosed herein animproved electromagnetic radiation emission device for generatingsubstantially black body electromagnetic radiation. In this invention, acavity electromagnetic radiation emission source is provided in a bodymember. The body member is fabricated from a material resistant to theflow of electrical energy therethrough so that upon the flow ofelectrical energy through the body member, it is heated. Electricalleads are connected at preselected spaced apart locations on the bodymember, so that as the electrical energy flows between the connections,the entire body member, including the walls defining the cavity, areheated in a predetermined pattern. The electrical cross-section of thebody member between the electrical connections is preselected to give apredetermined heating characteristic, and, therefore, radiation emissioncharacteristic from the cavity.

This invention relates to the electromagnetic radiation emission art andmore particularly to an improved electromagnetic radiation emissiondevice.

In the calibration, testing and utilization of many electromagneticradiation emission responsive systems, such as various infrared systemsand the like, there is often a requirement for providing a source ofelectromagnetic radiation emission having predetermined spectralcontent. Often, it is desired that such an electromagnetic radiationemission device be adapted to emit electromagnetic radiation at a hightemperature in order to provide a comparatively large amount of energyin any given electromagnetic radiation band width.

Prior art electromagnetic radiation emission devices, as far asapplicant is aware, have generally required external heating means suchas a coil, induction heater or the like, in order to heat the bodymember containing generally, a cavity type electromagnetic radiationemission source. Since these devices are, more or less, indirectlyheated, they have not always been able to provide the desiredelectromagnetic radiation emission pattern distribution in certainapplications or a precise temperature control.

Accordingly, it is an object of applicants invention herein to providean improved electromagnetic radiation emission device.

It is another object of applicants invention herein to provide anelectromagnetic radiation emission device in which the temperature ofthe radiating surface may be provided to obtain any pre-selectedelectromagnetic radiation pattern distribution.

It is yet another object of applicants invention herein to provide anelectromagnetic radiation emission device in which secondary heatingmeans are not required to provide a high temperature for the emission ofelectromagnetic radiation.

The above and other objects are achieved, according to one aspect ofapplicants invention, by providing a body member fabricated from anelectrically conductive mixture adapted to withstand high temperaturesand remain intact throughout comparatively long operating times at suchhigh temperatures. To the best of applicants knowledge, no suchutilization of the materials, as hereinafter set forth, has heretoforebeen made.

The body member is preferably made from a mixture of for example,aluminum oxide in a range of 10% to by weight and a material such as maybe selected from the class consisting of Kanthal metal, Nichrome,platinum, carbon, silicon carbide, silicon and germanium. Ceramicmaterials may also be utilized in the place of aluminum oxide, ifdesired. While ceramic-metal combinations, commonly called Cermets havebeen known in the past, applicant knows of no application Where theyhave been utilized for this particular application providing anelectrically conductive body member in an electromagnetic radiationemission device.

Electrical terminals are provided on the body member in a spaced apartrelationship, for example, at a first end and a second end thereof. Thefirst end of the electrically conductive body member in this embodimenthas walls defining a cavity extending a preselected distance into theelectrically conductive body member. In this embodiment of applicantsinvention, the electrical cross-section area contour of the electricallyconductive body member between the electrical terminals is preselectedso that a given pattern distribution of electromagnetic radiation willbe emitted from the walls defining the cavity. Thus, for example, theelectrical cross-sectional area contour between the two electricalterminals may be constant, that is, the cross-sectional area throughoutthe length of the body member is constant. In other embodiments ofapplicants invention, the electrical cross-sectional area contour may bevaried to provide any desired temperature distribution along the wallsdefining the cavity. However, applicant has found that, in general, toachieve black body radiation, it is generally preferable to have theelectrical cross-sectional area contour constant between the twoelectrical terminals.

Electrical energy is then supplied to the two electrical terminals andsince the electrical body member, is itself a conductor, there is acurrent flowing in the electrically conductive body member. However, theelectrical properties of the electrically conductive body member aresuch that it is heated by the passage of the electric current thereto.Thus, the electrical energy may be supplied for as long as is necessaryto heat the electrically conductive body member to any desiredtemperature for the emission of electromagnetic radiation from the wallsdefining the cavity.

In other embodiments of applicants invention, the electrical terminalsare supplied along oppositely disposed external peripheral longitudinallocations and the electrical cross-sectional contour is then provided inlongitudinally disposed cross-sections between the two electricalterminals.

The above and other embodiments of applicants invention may be morereadily understood from the following detailed description takentogether with the accompanying drawing wherein similar referencecharacters refer to similar elements throughout and in which:

FIGURE 1 and FIGURES 2A, 2B, 2C and 2D illustrate on embodiment ofapplicants invention;

FIGURES 3, 4 and 5 illustrate another embodiment of applicantsinvention; and

FIGURES 6A, 6B, 6C and 6D illustrate other embodiments of applicantsinvention.

Referring now to FIGURES 1 and 2A, 2B, 2C and 2D, there is shown oneembodiment of applicants invention for an improved electromagneticradiation emission device generally designated .10. As shown, theelectromagnetic radiation emission device 10 has a body member 12 with afirst end 14 and a second end 16. The first end 14 has walls 18 defininga cavity 20 extending a preselected distance into the body member 12.The walls 13 defining the cavity 20 comprise a cavity electromagneticradiation emission source adapted to emit electromagnetic radiationtherefrom as indicated by the arrow 22. While shown as a conical cavity,it will be appreciated that any desired cavity shape may be utilized.

A first electrical terminal 24 and a second electrical terminal 26which, in this embodiment of applicants invention, comprise ringlikemembers, are coupled to the electrically conductive body member 12 andthe first electrical terminal 24 is adjacent the first end 14 thereofand a second electrical terminal 26 is adjacent the second end .16, ofthe electrically conductive body member 12. The first electricalterminal 24 and the second electrical terminal 26 are powered by asource of alternating current 28 which, for example, may be conventional115 volt, 60 cycle alternating current, and power to the electricallyconductive body member 12 through the electrical terminals 24 and 26 iscontrolled by a switch means 30. It will be appreciated that this is aschematic representation of one means of controlling the electricalcurrent passing through the electrically conductive body member 12 andthat the precise means for controlling this current is not part ofapplicants invention herein.

In the embodiment of applicants invention shown in FIGURE 1, theelectrically conductive body member 12 has a preselected electricalcross-sectional area contour between the first electrical terminal 24and the second electrical terminal 26. The contour may be selected toprovide any desired pattern of heating of the walls 18 and, for example,the contour may be substantially a constant electrical cross-sectionalarea so that electromagnetic radiation 22 is emitted in a substantiallyblack body pattern distribution. FIGURES 2A, 2B, 2C and 2D illustratethe cross-sectional area of the electrically conductivebody member 12 atvarious cross-sectional points thereof, as indicated. Thus, thecross-sectional area shown in FIG- URES 2A, 2B, 2C and 2D issubstantially constant and at all points the cross-sectional area ofbody member 12 between the electrical connector 24 and the electricalconnector 26 is equal. Applicant has found that this provides asubstantially uniform temperature for the walls 18 to provide a closelycontrolled electromagnetic radiation emission 22 in a substantiallyblack body pattern distribution. It will be appreciated, however, thatany other electrical cross-sectional area contour may be selected toprovide any radiation pattern distribution from the walls 18 that may berequired.

In order to monitor the electromagnetic radiation emitted from theelectrically conductive body member 12, applicant may provide; a testelectromagnetic radiation emission source 32 defined by wall portions 34in the second end 16 of the electrically conductive body member 12.Electromagnetic radiation 36 emitted from the wall portions 34 in adirection substantially opposite to the direction of emission ofelectromagnetic radiation 22 from the cavity 20 may be monitored anddetected and utilized to control the amount of electrical energy flowinginto the electrically conductive body member 12 from the electricalterminals 24 and 26 in a manner described in my copending patentapplication, Ser. No. 521,- 045, filed concurrently herewith on J an.17, 1966. Further, appropriate shielding in the way of thermallyinsulating sleeves, apertures, and the like, as shown, for example, inthe above-mentioned copending patent application may also be utilized,as desired, in arrangements incorporating applicants invention herein.

While the walls 18 which emit the electromagnetic radiation are shown asdefining a conical cavity, it will be appreciated that any other desiredgeometric shape may be utilized as the surface for emitting radiation.For example, the shape defined by the walls 18 may be hemispheric asshown in FIG. 6A, hyperhemispheric, as

shown in FIG. 6B, cylindrical, as shown in FIG. 6C or even fiat, asshown in FIG. 6D.

As noted above, applicant utilizes in this invention an electricallyconductive body member 12. That is, the body member itself is at leastpartially electrically conductive and, preferably, is a comparativelypoor electrical conductor in order that it may more readily heat uponthe passage of an electric current therethrough. Further, sinceapplicants invention herein is often utilized to provide electromagneticradiations and comparatively high temperature surfaces, it is desirablethat the body member 12 remain intact and structurally integral overcomparatively long extended periods of operation at comparatively hightemperatures. Therefore, applicant has found that the body member 12when specifically designed to be operable at high temperatures ispreferably fabricated from a mixture comprising between 10% and byweight aluminum oxide and between 90% and 10%, correspondingly, of aconductor or semi-conductor of electricity which may be selected fromthe class consisting of Kanthal metal, Nichrome, platinum, carbon or thesemiconductors such as silicon carbide, silicon or germanium. When theelectrically conductive body member 12 is fabricated from thesematerials in the proportions listed, applicant has found that theelectrically conductive body member 12 rapidly heats upon application ofan electric current and remains substantially intact at evencomparatively high temperatures.

In the embodiment shown above on FIGURES 1 and 2A, 2B, 2C and 2D, it isseen that the electric current flows substantially axially, that is,along the long dimension of the cavity 20, which cavity may, if desired,be substantially conical in form, or in the forms shown on FIGURES 6A,6B, 6C or 6D.

Applicant has found, however, that applicants invention herein may alsobe practiced with other configurations of the body member 12 andpositioning of the electrical terminals 24 and 26. It is only necessaryin practicing applicants invention that the body member have apreselected electrical cross-section area contour between the twoelectrical terminals. FIGURES 3, 4 and 5 illustrate another embodimentof applicants invention, wherein the electric current flows atsubstantially right angles to the long axis of a cavity. In thisembodiment of applicants invention shown in FIGURES 3, 4 and 5, there isa preselected electrical cross-sectional area contour between the twoelectrodes, but it is not necessarily constant.

As shown therein, there is a body member 40 which may be fabricated fromthe same material as described above for the electrically conductivebody member 12. Electrically conductive body member 40 has a first end42 and a second end 44. The first end 42 has wall portions 46 defining asubstantially conical cavity 48, which may, if desired, be in any othergeometric shape, such as, for example, the shapes shown in FIGS. 6A, 6B,6C and 6D, and the wall portions 46 are adapted to emit electromagneticradiation 50 in a preselected direction. The second end 44 may, ifdesired, be provided with wall portions 52 defining a testelectromagnetic radiation source 54 that may be utilized in the controlof the temperature of the body member 40 as described in my copendingpatent application, Ser. No. 521,045, filed concurrently herewith on Jan. 17, 1966.

In this embodiment of applicants invention, there is provided a firstelectrical terminal 56 and a second electrical terminal 58 coupled tothe electrically conductive body member 40, along opposite externalperipheral longitudinally disposed surface portions 60 and 62 of theelectrically conductive body member 40.

Since the electrical terminals 56 and 58 are longitudinally disposedwith respect to the long axis of the cavity 48, in this embodiment ofapplicants invention, it is preferred that there be a predeterminedelectrical crosssectional area contour be we n the electrical terminals56 and 58. Thus, as shown on FIGURE 4, the electrical cross-sectionalarea, for example, as indicated by the dotted lines 64 should have thispreselected electrical cross-sectional area contour. For example, thecontour may be selected so that the cross-sectional area along each ofthe planes indicated by the lines 64 is substantially constant, or itmay vary in any desired predetermined manner. In any event, theparticular preselected electrical cross-sectional area contour that isdetermined for the body member is such that the electromagneticradiation emitted from the wall portions 46 has a predetermined patterndistribution.

In the operation of applicants invention as shown on FIGURES 3, 4 and 5,electrical energy is supplied from a source of alternating current 66which, for example, may be conventional 115, volt, cycle alternatingcurrent, and it is controlled by, for example, a switch means 68 so thatelectrical current flows between the electrical terminals 56 and 58 fora time period sufiicient to heat the body member 40 to any desiredtemperature. It will be appreciated that the showing of the switch 68and the source of electrical energy 66 is a more or less conventionalrepresentation and that applicants invention may equally well beutilized with more sophisticated control systems for controlling thetemperature of the electrically conductive body member 40.

This concludes a description of applicants invention of an improvedcavity electromagnetic radiation emission device. Those skilled in theart may find many variations and adaptations of applicants inventionherein and the following claims are intended to cover all suchvariations and adaptations falling within the true scope and spirit ofapplicants invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. An electromagnetic radiation emission device comprising incombination;

an electrically conductive body member having a first end and a secondend;

said first end of said electrically conductive body member having Wallsdefining an electromagnetic radiation emitting surface having apreselected geometric shape;

a first and a second electrical terminal coupled to said body member ina spaced apart relationship;

and said body member having a preselected electrical cross-section areacontour between said first and said second electrical terminals wherebyelectrical energy is supplied to said electrically conductive bodymember from said terminals for heating said body member and said wallsthereof to provide electromagnetic radiation emitted therefrom in apredetermined pattern distribution.

2. The arrangement defined in claim 1 wherein said predeterminedcross-sectional contour of said electrically conductive body member isconstant, said preselected shape is conical and said electromagneticradiation emitted from said walls defining said surface is emitted in asubstantially black body pattern distribution.

3. The arrangement defined in claim 2 wherein said first and said secondelectrical terminals comprise ring like members engaging saidelectrically conductive body member adjacent to said first end and saidsecond end, respectively.

4. The arrangement defined in claim 2 wherein said first and said secondterminals comprise means engaging said body member in oppositelydisposed external peripheral longitudinally aligned locations.

5. The arrangement defined in claim 1 wherein said electricallyconductive body member is comprised of between approximately 10% and 90%aluminum oxide and between approximately 90% and 10%, correspondingly,of material selected from the class consisting of Kanthal metal,Nichrome, platinum, carbon, silicon carbide, silicon and germanium.

6. The arrangement defined in claim 5 wherein said first and said secondelectrical terminals comprise ringlike members engaging saidelectrically conductive cylindrical body member adjacent said first endand said second end thereof, respectively.

7. Arrangement defined in claim 5 wherein said first and said secondelectrical terminals comprise means engaging said body member inoppositely disposed external peripheral locations, and said preselectedelectrical cross-sectional area contour comprises cross-sectional areasparallel thereto.

8. The arrangement defined in claim 6 wherein said predeterminedcross-sectional contour is constant, said preselected geometric shape isconical and said electromagnetic radiation emitted from said cavity isemitted in a substantially black body pattern distribution.

9. The arrangement defined in claim 7 wherein said preselectedelectrical crossasection contour is constant and said electromagneticradiation emitted from said walls defining said cavity is emitted in asubstantially black body pattern distribution.

10. The arrangement defined in claim 1 wherein said preselectedelectrical cross-sectional contour provides substantially constanttemperature throughout said walls defining said electromagneticradiation emission surface.

References (Zited UNITED STATES PATENTS 2/1961 Calvert. 9/1965 Kauer eta1.

OTHER REFERENCES RALPH G. NILSON, Primary Examiner S. C. SHEAR,Assistant Examiner US. Cl. X.R. 219502

